1. Field of the Invention
The present invention relates to an ink-jet recording apparatus and a method for controlling the same. In particular, the present invention relates to an ink-jet recording apparatus which performs a purge process for discharging an ink from nozzle holes in a state in which the nozzle holes are tightly closed and which performs a flashing process for discharging the ink irrelevant to the recording operation, and a method for controlling the same.
2. Description of the Related Art
As disclosed in Japanese Patent No. 3293765 (for example, FIG. 5), an ink-jet recording apparatus is known, in which the occurrence of printing failure or the like is avoided by executing the cleaning process comprising, for example, the ink suction process (purge process) for forcibly sucking the ink from the recording head in order to discharge, for example, bubbles and the ink having an increased viscosity in the nozzle holes of the recording head, and the flashing process for forcibly discharging the ink from the nozzle holes of the recording head. In the cleaning process, the purge process is performed, in which the recording head is sealed by a cap and the ink is sucked by driving a suction pump. When the purge process is completed, the cap is released from the recording head to perform the wiping process in which the ink adhered around the nozzle holes is wiped out by using a wiper. After that, in order to discharge the ink having been forcibly introduced into the nozzle holes by the wiping process, the flashing process is performed, in which the ink is discharged from the nozzle holes by driving the recording head.
However, in the case of the ink-jet recording apparatus in which the cleaning process is executed as described above, bubbles are formed in the cap, because the ink is spread by the purge process at a high speed from the nozzle hole having the small diameter into the cap. When the purge process is stopped, the bubbles contained in the cap are pulled into the nozzle hole by the negative pressure (back pressure) acting on the ink in the recording head from the ink supply source. If the flashing process is performed in this state, the bubbles are consequently grown by the sudden repetition of the negative pressure and the positive pressure acting on the ink by the driving of the recording head. In particular, in the case of an ink supply source, i.e., an ink cartridge to be used several days after the opening of the package, the air is dissolved in the ink, and the degassing degree is lowered. Therefore, the air dissolved in the ink further facilitates the growth of the bubbles. The bubbles as described above act during the recording operation such that the nozzle holes are closed, and the discharge pressure, which is brought about by the driving the recording head, is absorbed, resulting in the occurrence of discharge failure of the ink.
In the case of Japanese Patent No. 3293765, a predetermined pause time is provided to spontaneously extinguish the bubbles contained in the recording head prior to the flashing process after completion of the purge process. Then, the flashing process is performed to suppress the growth of the bubbles thereby so that the ink discharge failure is decreased. However, this processing step involves the following problem. That is, it is necessary to secure the predetermined pause time between the purge process and the flashing process, and hence the period of time required for the cleaning process, which includes the pause time, inhibits the use of the ink-jet printer to be operated by the user. In other words, if the user intends to perform the printing by using the printer during the cleaning process including the pause time, it is necessary to wait until the completion of the process, which causes the stress for the user.